It is known earlier to make surfaces more wear resistant and corrosion resistant by coating them with an abrasion resistant material. Such hard metal coatings usually consist of Ni- and Co-alloys, which form a softer binding phase and in addition contain hard particles such as oxides, carbides, borides and nitrides. The hard particles may either be mixed with the binding phase or oxygen, carbon, nitrogen and/or boron are added in such amounts that these form oxides, carbides, nitrides and/or borides. The abrasion resistant material is usually applied to the surface that should be treated in the form of a powder. The powder is applied to the surface and the binding phase is melted. Alternatively the material may already be melted when it is applied to the surface.
Coating material with a binding phase consisting of a Ni- or a Co-alloy may cause problems in that the coated surface in many instances is more noble than the parent metal which may give rise to galvanic corrosion. These coating materials are also relatively expensive.
Today there are also coatings of stainless steel for certain applications. The surfaces which shall be protected are coated with stainless steel, either by thermal spraying or by welding the stainless steel. There are certain drawbacks. If the stairdess steel is added by thermal spraying there is no tight layer. If the stainless steel is welded, the material which is to be coated melts.